The present invention relates to improving the heat transfer capabilities of a tube bundle to be used in a shell and tube heat exchanger. In another aspect, the invention relates to tightening a tube bundle to mitigate or eliminate damage caused by vibrations. In still another aspect, the invention relates to assembling a rigid tube bundle to mitigate or eliminate in-use damage to the bundle caused by vibrations. In still another aspect, the invention relates to a modified plate baffled tube bundle which has increased heat transfer with a minimal increase in pressure drop. In yet another aspect, the invention relates to novel heat exchanger baffles.
Heat transfer is an important part of any process. As is well known, an indirect transfer of heat from one medium to another is usually accomplished by the use of heat exchangers, of which there are many types. For example, there are double pipe, shell and tube, plate heat exchangers and others. Indeed, the art of heat exchanger design is developed to a very high degree. However, there is still room for improvement in a number of areas, such as in reducing pressure drop, increasing heat transfer coefficients, reducing fouling, and, especially in shell and tube exchangers to prevent damage resulting from vibrations, for example, wherein finned tubes and/or plate baffles are employed.
In most plate baffle type heat exchangers, the passages in the plate baffles through which the tubes pass are slightly larger in diameter than the outside diameter of the tubes in order to facilitate construction of the tube bundle. It is known that the heat transfer coefficient of such a bundle can be improved by employing finned tubes in the tube bundle. However, in a very popular species of finned tubes, the plain end diameter of the tube is larger than the diameter of the finned portion of the tube. Since the passages through the plates must be sufficiently large to permit passage of the plain end of the tube for construction of the exchanger, the result is an excessive space between the walls of the passages through the plates and the surface of the finned section of the tube. This excessive space permits tube vibration to occur when the heat exchanger is in use which frequently results in premature tube failure.
Rod baffles, such as disclosed in U.S. Pat. No. 4,136,736, provide the tubes in the tube bundle with complete radial support and substantially reduce tube damage caused by vibration. However, it has been difficult to construct a tube bundle using finned tubes with rod baffles to prevent vibratory damage of the tubes when the heat exchanger is utilized.
It would be desirable in tube bundles which employ plate baffles to further improve their heat transfer coefficient without incurring a substantial increase in pressure drop.